0:12Skip to 0 minutes and 12 secondsOne of the issues that people face when they lose weight is the problem of actually keeping it off. So although we know how people can lose weight-- and a lot of people are very successful at that-- the majority of people do experience weight rebound. And over two or three years after losing a substantial amount of weight, unfortunately, the majority of people will regain it. So this is obviously quite depressing for people and is not a great outcome for them. So there has been quite a lot of work done on the reasons why people regain weight. And some of it's about our physiology, that our bodies defend a set point in our weight.

0:50Skip to 0 minutes and 50 secondsSo in other words, it decides what weight you're going to be and then it actively defends that position. So if you lose weight, it tries to get you back to where you were. And it's a combination of your brain and your gut. So your gut hormones send signals to your brain telling you that you're more hungry and that you want to eat more. So consequently, obviously if you in a reduced weight state, if you eat more, you're going to start gradually gaining that weight back on. So it is hard for people to actually maintain lost weight. But we can learn things from people who are successful at this.

1:27Skip to 1 minute and 27 secondsAnd we've learned from people who have lost weight and maintained weight loss for more than a year. And we know certain things, they have certain characteristics. So these characteristics are one, they self monitor their weight regularly. So in other words, they'll weight themselves at least once a week, maybe twice a week. And if they've gained a little bit of weight, they're active about losing that weight again, so they don't get that weight creeping upwards. Two, they're reasonably active. It's not major amounts of physical activity, but it's basically walking. And people need to do at least half an hour to an hour a day, of trying to maintain a physical activity level.

2:07Skip to 2 minutes and 7 secondsThe other things, in terms of diet, that successful weight loss maintainers do is that they eat breakfast, they tend to eat regular meals, and they tend to have the same food. So in other words, people get into a bit of a pattern and a bit of a rhythm about this is what I have for breakfast, this is what I have for my morning snack, this is what I have for lunch. And people's evening meal might vary a bit, but the amount and quantity of food that they eat doesn't vary too much. So those seem to be some tips that really help people be successful in maintaining weight lost.

2:42Skip to 2 minutes and 42 secondsSo this theory of set point weight would seem to indicate that people find it difficult to reset that weight point. And once people have become obese, it's really difficult for them to actually maintain a lower weight. So it's not necessarily because people don't try. It's that physiologically it's very difficult for them. And I think we need to recognize that more in society, about how hard it is for people to actually maintain weight lost. It's not impossible, but it's certainly quite difficult for people to do.

3:12Skip to 3 minutes and 12 secondsSo one of the reasons why we're moving more towards prevention of weight gain is that, obviously, if you don't reach that obese state, then it's easier for you to have a physiological set point that's lower. So there are key times in our lives when we know people are more susceptible to weight gain. And in women, it's particularly around pregnancy and between pregnancies. So people gain weight when they're pregnant. Obviously then they lose weight, hopefully, during breastfeeding times and when their babies are small. If they don't go back to their original weight and they get pregnant again, that tends to be a period of time where people will continue to gain weight. And it's very hard.

3:52Skip to 3 minutes and 52 secondsSo there are key times when people perhaps can be more sensitive about trying to reduce their weight back to what it was before they were pregnant, before they have another baby. So those strategies might help certain groups of people, but it is difficult, and it's not something that we entirely understand about how we might be able to reset people's point for weight. It's not impossible, but it's certainly challenging for most people.

Weight regain: why does this happen so often?

Watch Helen talk about weight loss and the role our mind and body play in weight regain.